1. Field of the Invention
The present invention relates to new maloaluminate compositions of matter and to oral compositions containing such materials that are effective in reducing the incidence and severity of dental caries.
2. Description of the Prior Art
It is commonly recognized that the presence of small amounts of fluoride occurring naturally in drinking water (e.g., 1.0 microgram fluoride per milliliter) has a pronounced effect in reducing the incidence of dental caries in permanent teeth of children consuming such water from birth through eight years of age. Fluoride salts have been introduced into public water supplies in many communities with similar results. This method of dental caries prophylaxis is not available, however, to large numbers of people whose drinking water is obtained from small, private, fluoride-deficient sources such as individual wells and the like. Further, the addition of fluoride to common public water sources is not always accepted or permitted.
Topical application of aqueous fluoride solutions by dentists or dental hygienists likewise provides an excellent measure of protection against dental caries. Various fluoride compounds have been employed in this manner, including stannous fluoride and sodium fluoride. Another method of employing the anticariogenic properties of fluoride salts comprises incorporating such materials with a compatible abrasive to form a prophylactic paste composition for use by dentists or dental hygienists on a professional basis.
Limitations on the availability of fluoride therapy by way of water supply or professional treatment has led to extensive efforts to incorporate fluoride salts in oral compositions of use in the home in the form of fluoride-containing dentifrices. Although effective dental caries protection has been obtained through the use of the aforementioned fluoride-containing compounds, occasional side effects have been experienced with certain of the known fluoride-containing anticariogenic agents, particularly certain tin-containing salts. For example, a brownish pigmentation of carious or precarious lesions has been experienced after anticariogenic agents containing the stannous ion have been applied to the teeth when the teeth are not properly cleaned with a toothbrush. Although the stain is not necessarily undesirable from a physiological standpoint, nevertheless, for aesthetic reasons it would be desirable to provide an effective anticariogenic agent that does not pigment carious enamel.
The utility of certain of the prior art anticariogenic fluoride materials has also been limited by the extent of their solubility in aqueous media. For example, sodium fluoride is only soluble to the extent of about 4% in water.
Furthermore, because of the concern from a toxicity standpoint, current regulations imposed by the U.S. Food and Drug Administration limit the amount of fluoride that can be provided in products sold for over-the-counter use.
Finally, certain of the known prior art anticariogenic agents have been relatively unstable in aqueous solution. For example, stannous fluoride is subject to both oxidation and hydrolysis and for that reason must be used in freshly prepared form and must be used in conjunction with complexing anions in order to obtain its optimal anticariogenic effect.
For the foregoing and other reasons, dental researchers have continued their efforts to develop new, non-fluoride anticariogenic agents which demonstrate a high level of anticariogenic effectiveness as compared to fluorides but which are non-toxic, stable, and widely available. It has been suggested that aluminum salts may have a beneficial effect in reducing dental caries itself or in facilitating the uptake of fluoride by the dental enamel. See, e.g., Manly et al., "Substances Capable of Decreasing the Acid Solubility of Tooth Enamel", J. Den. Res. 28: 160 (1948); Regolati, et al., "Effects of Aluminum and Fluoride on Caries, Fluorine Content and Dissolution of Rat Molars", Hel. Odont. Acta. 13: 59 (1969); and on "Electrochemical Characteristics of Free and Complexed Fluorides in Drinking Water and The Effects of Aluminum and Iron on Fluoride Incorporation Into Tooth Enamel, Univ. Michigan Thesis (1972).
In vitro studies have shown that pretreatment of enamel with aluminum solutions resulted in increased fluoride uptake when followed by treatment with a fluoride solution; however, treatment with combinations of aluminum and fluoride did not afford any added benefit over that of fluoride alone. McCann, "The Effect of Fluoride Complex Formation of Fluoride Uptake and Retention in Human Enamel", Archs. Oral Biol. 14:521 (1969); and Gerhardt, et al., "Fluoride Uptake in Natural Tooth Surfaces Pretreated with Aluminum Nitrate", J. Dent. Res. 51:870 (1972). Moreover, the foregoing techniques have dealt primarily with the use of aluminum in combination with fluorides in acidic media and have not focussed on the effect of aluminum in the absence of fluoride and in alkaline media.
Thus, while some elements are known to inhibit dental caries (e.g., F, Mo., Sr, and V) and while others are known to promote dental caries (e.g., Se, Mg, and Cd), the preponderance of data on aluminum indicate that it is dental caries inert as classified by Navia, "Effect of Minerals on Dental Caries", in Dietary Chemicals vs. Dental Caries, A.C.S., Washington, D.C. (1970).
Nor has the use of aluminum salts in dentifrices demonstrated the desired result, primarily because they have failed to recognize that conventional dentifrice constituents such as abrasives are incompatible with sources of biologically available aluminum. Thus, while French Pat. No. 3610M describes a specific combination of aluminum lactate, aluminum fluoride and calcium pyrophosphate, the abrasive interferes with the aluminum by reacting therewith to form insoluble aluminum phosphate, Similarly, U.S. Pat. No. 3,195,356 uses aluminum salts such as aluminum fluoride to coact with insoluble sodium metaphosphate abrasives to reduce the solubility of such abrasives and to increase fluoride uptake, but without independent therapeutic advantage being taken of the aluminum.
U.S. Pat. No. 3,282,792 describes low pH stannous fluoride dentifrices stabilized against precipitation and oxidation of stannous tin ions through the use of hydroxyl substituted di- and tri-carboxylic acids. However, nothing is said in the patent regarding the use of aluminum with respect to anticariogenic systems that do not contain fluoride. Similarly, while U.S. Pat. No. 3,937,806 teaches oral compositions comprising indium and fluoride to which malic acid is added to stabilize the indium, the patent does not recognize that beneficial results may be achieved with aluminum and carboxylic acids without incorporating fluoride.
Canadian Patent No. 928,272 describes acidic dentifrices comprising a combination of surface active substances and albumencoagulating substances such as certain carboxylic acid salts of aluminum and other metals. However, this patent likewise fails to teach that significant dental health benefits can be achieved with alkaline aluminum systems. And while the reaction of aluminum chloride and ammonium malate in varying ratios at different pH's has been studied (Kalalova, "Disintegration of Compounds of Aluminum with Malate-Anion Through Warming", Scientific Papers of the Institute of Chem. Tech. Prague B(17) 1973 Inorganic Chem, and Tech. p. 167), the author failed to isolate a stable aqueous maloaluminate complex existing at pH greater than 7.0 and less than 9.0 nor is any suggestion made as to possible dental utility of such material in oral compositions.
Thus, the prior art has as yet not developed a stable alkaline system providing biologically available aluminum in anticariogenic oral compositions.
Accordingly, it is a primary object of the present invention to provide a new composition of matter effective in reducing the incidence and severity of dental caries.
A related object is to provide new anticariogenically effective non-fluoride oral compositions.
Another object is to provide new maloaluminate complexes which are effective in weakly alkaline oral compositions.